Fix overriding Fast Image/Video Processors instance attributes affect other instances

[yonigozlan]

What does this PR do?

Fix an issue raised here #39172 (comment)
After internal discussions with @ydshieh , we found that the issue is not due to class attributes, but to lists/dicts being passed around without being copied.
In fact the same issue is also present in slow image processors, but we don't fix them here, as they all have their own attributes assignment logic, and are to be deprecated.

To reproduce the issue:

>>> o = CLIPImageProcessorFast()
>>> o.image_mean[0]
0.48145466
>>> CLIPImageProcessorFast.image_mean
[0.48145466, 0.4578275, 0.40821073]
>>> o.image_mean[0] = 1
>>> CLIPImageProcessorFast.image_mean
[1, 0.4578275, 0.40821073]
>>>

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[ydshieh]

if I understand correctly the purpose here, maybe the above block should be

        for key in image_processor_2.size:
            image_processor_2.size[key] = -2
        image_processor_2.image_mean[0] = -2

(or anything that is not -1)??

[yonigozlan]

Ah yes of course 😅, thanks

[ydshieh]

Hopefully no edge case we will find in tomorrow's CI 😅

Thank you a lot, especially adding the test